2015 Jeep Cherokee Spark Plug Type & Gap Guide

As an ASE-certified master technician, I’ve pulled thousands of spark plugs from modern engines. If you’re working on a 2015 Jeep Cherokee, you’re dealing with a modern, computerized powertrain that is highly sensitive to ignition health. Whether you have the 2.4L Tigershark inline-four or the 3.2L Pentastar V6, installing the correct spark plugs with the precise gap and torque is non-negotiable for maintaining fuel economy, preventing misfires, and keeping the check engine light off.

Here is your comprehensive guide to the spark plug specifications, replacement procedures, and pro tips for the 2015 Jeep Cherokee.

Quick reference

Note: Always verify the exact part numbers with your vehicle's VIN, as mid-year production changes can occasionally alter requirements.

Why the right plug matters

Modern Jeeps are engineered with extremely precise ignition timing and fuel delivery mapping. Using the correct spark plug matters primarily for two reasons: heat range and electrode material.

The heat range determines how fast the plug pulls heat away from its firing tip. A plug that runs too hot will cause pre-ignition and engine knock, while a plug that runs too cold will foul with carbon deposits.

Additionally, the 2015 Jeep Cherokee engines require Iridium spark plugs. Iridium is significantly harder and more durable than traditional copper or platinum. Because of the coil-on-plug ignition systems used in both the 2.4L and 3.2L engines, high-energy voltage is sent directly to the plug. Copper or platinum plugs will erode too quickly under this stress, leading to a widened gap, misfires, and reduced fuel economy well before the 100,000-mile service interval.

How to gap a spark plug

While modern Iridium spark plugs typically come pre-gapped from the factory, an ASE tech will tell you to always verify the gap before installation. A box can easily be dropped in transit, closing the gap.

1. Use a wire-style gauge: Do not use the cheap coin-style gauges on Iridium plugs. The delicate center electrode can easily snap off. Use a wire-loop gauge.
2. Measure gently: Slide the correct size wire between the center and ground electrode. It should slide through with a slight drag.
3. Adjusting the gap: If the gap is too tight, use the adjustment tool (often attached to the gauge) to gently bend the ground strap away from the center electrode. Never pry against the Iridium center tip.

Replacement procedure tips

Replacing plugs on the 2015 Jeep Cherokee presents different challenges depending on your engine:

• 2.4L Tigershark: This is a straightforward inline-four. Remove the engine cover, unbolt the 10mm fasteners holding the coil-on-plug boots, pull the coils, and use a 5/8-inch spark plug socket on an extension to remove the plugs.
• 3.2L Pentastar V6: This job is significantly more labor-intensive. While the front three cylinders are easily accessible, the upper intake manifold (plenum) must be removed to access the rear bank of cylinders against the firewall.
• The Anti-Seize Debate: Most modern NGK and Denso plugs feature trivalent metal plating, which acts as a built-in release agent. Do not apply anti-seize to these threads, as the lubrication will cause you to over-torque the plug, potentially stripping the aluminum cylinder head.
• Dielectric Grease: Always apply a small dab of dielectric grease to the inside of the coil boot before snapping it onto the new plug. This prevents moisture intrusion and stops the rubber boot from baking onto the plug's porcelain over the next 100,000 miles.

Known issues

While you won't face the infamous broken 2-piece spark plug nightmare of older Ford 3-valve engines, the Jeep Cherokee does have a few quirks to watch out for during this service:

• Oil in the spark plug tubes: When pulling your ignition coils, inspect the rubber boots for engine oil. The valve cover gaskets and spark plug tube seals on the 2.4L and 3.2L are prone to leaking as they age. If the boot is soaked in oil, replacing the plugs isn't enough; you must replace the valve cover gasket and tube seals to prevent the oil from shorting out the new ignition coils.
• Intake Manifold Gaskets (3.2L): Because you have to remove the upper intake plenum to do the rear plugs on the V6, always replace the upper intake manifold gaskets. Reusing the old, compressed rubber gaskets will result in a vacuum leak, causing a high idle and a P0171/P0174 Lean code.

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